You asked, "Is a magneto sparked, gravity fuel fed engine with no external need except air a reliable design? Or is a liquid cooled, electrical power dependent one more suitable?"

According to Mark Kettering (former aerospace engineer at NASA) a modern auto engine with fuel injection and single electronic ignition is far more reliable that an engine with two magnetos. Add in the possibility of carburetor failure and it gets even worse for the legacy engines.

this discussion seems to be going south now, so a(former aerospace engineer at NASA) is now an expert in internal combustion engines, claiming a single source failure mode is more reliable. I guess if the "expert" says so.

Proper failure analysis can (and does) predict with near certainty the overall chances of failure of various components and groups of components. One can choose to believe these statistics, or not. Personally I tend to give great weight to scientifically derived data, and far less weight to a single person's anecdotal experience. Others approach this differently. But it was you who asked the question. I merely attempted to give you an answer based on fact.

Don’t think the Viking gear box is a cobbled together bunch of parts. Jan’s gearbox is a well thought out and engineered PSRU.

I am a retired mechanical engineer with 44 years of machine design experience. I was very impressed with Jan’s Honda based engine which is why I have one in my Zenith 750.

Lycoming and continental have been around a long time and both have a well proven design. Still they are both based on 1930’s technology. Direct drive, air cooled, magneto ignition, with temperatures that range from below zero to upwards of 500 degrees F. Air cooling inherently is less efficient than liquid cooling and as a result has an extremely wide temperature range. Wide operating temperatures can cause their own problems is not well managed by the pilot. As a CFI who has been flying for over 50 years, I have seen a lot of pilots that haven’t a clue about the nuances of managing an air cooled engine. Many think it is just like there care. Get in, turn the key, and go fly with little regard to managing temperatures. Liquid cooled with an ECU can greatly reduce the pilot workload and potential engine abuse.

ROTAX has become the “Standard” engine in LSA with over 50,000 flying. It originated as as a snowmobile/jet ski engine and is a geared, air/water cooled hybrid.

Don’t think Honda is going to pursue the very small aviation market, just not economically worth it . Viking only has less than 1000 engines in the market place, but it is growing so it is a limited market.

The beauty of the experimental movement is we have the option to try lots of different ideas and we can think outside the traditional box. Jan is definitely an “outside the box” thinker with his conversion of a great Honda engine. Other “out of the box” thinkers are Burt Rutan, Vans, Chris Heinz, as were the Wright brother who all were stretching the boundaries of “traditional”.

my 1930's technology engine is powering my 1903 technology aircraft, just a few questions (inspired by your geared engine discussion ) What RPM did the Lycoming or Continental geared engines operate? what engine RPM is used in Viking cruise, how about when used in a car; what RPM at highway cruise? apparently the room maintains that this new technology is somehow safer and more reliable, I guess time will tell. When removing the previous car engine from my airframe I did consider Viking but did not want to deal with extensive fuel system rework

Your rpm questions seem to imply that because autos run at much lower continuous rpm, then pushing them to much higher continuous rpm would naturally be unadvised. This would be a natural response. However, you might be interested to know that Honda uses the same engine that Viking uses in their marine applications, where continuous rpm is right up there with aircraft applications (as well as coupling them to gear reduction).

I have about 34 hours on my VIking on a Zenith 750, another fried finished his air-cooled airplane about the same time. We both had some temperature issues with our cowls soon after first flights, I was able to add some ducting and wrapped the exhaust and now I have almost unlimited ability to use WOT on a hot day.

I had to tune for one number, the coolant temperature. My friend is weeks into his testing and still not able to leave the pattern dealing with head temperatures and balancing out his CHT across several cylinders.

This really simplified the equation. I also don't have to worry about carb heat or mixture and it starts every time without any though or effort. In hundreds of hours of flying Lycoming and Continental engines I maybe get one start in 4 on the first crank, and that usually involves a long sustained use of the starter, not the tiny blip you need on the Viking.

Certainly time will tell as to if I have any downsides to the technology, but so far I am really enjoying the advantages. Oh and with the money I saved I am enjoying that new-tech glass cockpit I could afford. :-)

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